Effects of noise exposure on young adults with normal audiograms II: Behavioral measures

Abstract

An estimate of lifetime noise exposure was used as the primary predictor of performance on a range of behavioral tasks: frequency and intensity difference limens, amplitude modulation detection, interaural phase discrimination, the digit triplet speech test, the co-ordinate response speech measure, an auditory localization task, a musical consonance task and a subjective report of hearing ability. One hundred and thirty-eight participants (81 females) aged 18-36 years were tested, with a wide range of self-reported noise exposure. All had normal pure-tone audiograms up to 8 kHz. It was predicted that increased lifetime noise exposure, which we assume to be concordant with noise-induced cochlear synaptopathy, would elevate behavioral thresholds, in particular for stimuli with high levels in a high spectral region. However, the results showed little effect of noise exposure on performance. There were a number of weak relations with noise exposure across the test battery, although many of these were in the opposite direction to the predictions, and none were statistically significant after correction for multiple comparisons. There were also no strong correlations between electrophysiological measures of synaptopathy published previously and the behavioral measures reported here. Consistent with our previous electrophysiological results, the present results provide no evidence that noise exposure is related to significant perceptual deficits in young listeners with normal audiometric hearing. It is possible that the effects of noise-induced cochlear synaptopathy are only measurable in humans with extreme noise exposures, and that these effects always co-occur with a loss of audiometric sensitivity.

Keywords: Cochlear synaptopathy; Hidden hearing loss; Noise-induced hearing loss; Psychophysics; Speech-in-noise.

Fig. 1

Noise exposure scores as a function of age for 137 participants. The regression line is plotted with the Pearson correlation coefficient shown in the text (* = 0.05, ** = p < 0.01).

Fig. 2

Pure tone audiometric thresholds (averaged across ears and listeners) are shown, with 95% confidence intervals, for the whole group and for the 25% of participants with the highest and lowest noise exposures.

Fig. 3

The four panels show the results of the four psychophysical tasks: Frequency difference limens (FDL), intensity difference limens (IDL), interaural phase difference discrimination (IPD), and amplitude modulation detection (AMD). Mean thresholds and 95% confidence intervals are plotted for the 25% of participants with the lowest and highest lifetime noise exposures for the four conditions of each task.

Fig. 4

Mean thresholds (and 95% confidence intervals) are shown for the DTT, CRMc and CRMo speech tasks. The SNRs required for 25%, 50% and 75% correct on the psychometric function are plotted for the 25% of participants with the highest and lowest noise exposures in black (closed) and green (open) symbols, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 5

Mean localization error (and 95% confidence intervals) for the 25% of participants with the lowest and highest noise exposures (green and black lines, respectively). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 6

Mean pleasantness ratings are shown (along with 95% confidence intervals) for the 11 dyads in the consonance task. Results for the 25% of listeners with the lowest and highest lifetime noise exposures are plotted in green and black, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Fig. 7

Mean ratings (and 95% confidence intervals) for the Speech, Spatial, and Qualities scales of the SSQ. Results for the 25% of listeners with the lowest and highest lifetime noise exposures are shown by green open squares and black solid squares, respectively. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)